On its way to the detector, the ion beam of an ion source passes a number of components whose design decisively influence the quality of the analysis by mass spectrometry. The so-called ion optical components for the guidance, the focusing and, if appropriate, the acceleration of the ion beam are of particular importance. Hitherto, aperture and lens systems made of steel have been used. A disadvantage of the material steel is that atoms and ions are released which, under unfavorable circumstances, are detected and interfere with the ions to be analyzed, or spoil their signals. The release of atoms and ions from a surface as a result of bombardment is also known as sputtering effect.
It is of crucial importance to avoid the sputtering effect in high resolution mass spectrometers in connection with an ICP-plasma ion source or an API ion source (ICP=Inductive Coupled Plasma, API=Atmospheric Pressure Ionization). At the exit of the ion source there is a very high ion current. The source itself is normally operated at atmospheric pressure. The inert gas, for example argon, used for the generation of the plasma can flow into the ion optical system in ionized form via an intermediate interface. A pressure reduction occurs over a plurality of stages until a high vacuum is reached, but there is a relatively high current of argon ions at the entrance of the ion optical system which favors the sputtering effect on the components of the ion optical system. The same applies to all other components that are subjected to the ion current, e.g. the sampler and the skimmer of the interface near the exit of the ion source.